| 1. |
- Humborg, Cristoph, et al.
(author)
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CO2 supersaturation along the aquatic conduit in Swedish watersheds as constrained by terrestrial respiration, aquatic respiration and weathering
- 2010
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In: Global Change Biology. - : Wiley. - 1354-1013 .- 1365-2486. ; 6:7, s. 1966-1978
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Journal article (peer-reviewed)abstract
- We tested the hypothesis that CO2 supersaturation along the aquatic conduit over Sweden can be explained by processes other than aquatic respiration. A first generalized-additive model (GAM) analysis evaluating the relationships between single water chemistry variables and pCO(2) in lakes and streams revealed that water chemistry variables typical for groundwater input, e.g., dissolved silicate (DSi) and Mg2+ had explanatory power similar to total organic carbon (TOC). Further GAM analyses on various lake size classes and stream orders corroborated the slightly higher explanatory power for DSi in lakes and Mg2+ for streams compared with TOC. Both DSi and TOC explained 22-46% of the pCO(2) variability in various lake classes (0.01-> 100 km2) and Mg2+ and TOC explained 11-41% of the pCO(2) variability in the various stream orders. This suggests that aquatic pCO(2) has a strong groundwater signature. Terrestrial respiration is a significant source of the observed supersaturation and we may assume that both terrestrial respiration and aquatic respiration contributed equally to pCO(2) efflux. pCO(2) and TOC concentrations decreased with lake size suggesting that the longer water residence time allow greater equilibration of CO2 with the atmosphere and in-lake mineralization of TOC. For streams, we observed a decreasing trend in pCO(2) with stream orders between 3 and 6. We calculated the total CO2 efflux from all Swedish lakes and streams to be 2.58 Tg C yr-1. Our analyses also demonstrated that 0.70 Tg C yr-1 are exported to the ocean by Swedish watersheds as HCO3- and CO(3)2- of which about 0.56 Tg C yr-1 is also a residual from terrestrial respiration and constitute a long-term sink for atmospheric CO2. Taking all dissolved inorganic carbon (DIC) fluxes along the aquatic conduit into account will lower the estimated net ecosystem C exchange (NEE) by 2.02 Tg C yr-1, which corresponds to 10% of the NEE in Sweden.
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| 2. |
- Pacini, N, et al.
(author)
-
Nutrient Processes and Consequences.
- 2008
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In: Ecohydrology; Processes, Models and Case Studies. - Oxford : Oxford University Press. - 9781845930028 ; , s. -391
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Book chapter (other academic/artistic)abstract
- This book contains 15 chapters dealing with the integration of ecology with hydrology at the river basin scale. The patterns and processes in the catchment including nutrients, lotic vegetation and aquatic faunal processes are covered. In addition, the benefits and risks of ecological modelling to water management and nutrient budget modelling for lakes and watershed restoration are discussed. The roles of ecohydrology in managing the savannah ecosystem, agricultural landscape, and watershed development are explored.
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| 3. |
- Zhang, J., et al.
(author)
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Natural and human-induced hypoxia and consequences for coastal areas : synthesis and future development
- 2010
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In: Biogeosciences. - : Copernicus GmbH. - 1726-4170 .- 1726-4189. ; 7:5, s. 1443-1467
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Journal article (peer-reviewed)abstract
- Hypoxia has become a world-wide phenomenon in the global coastal ocean and causes a deterioration of the structure and function of ecosystems. Based on the collective contributions of members of SCOR Working Group #128, the present study provides an overview of the major aspects of coastal hypoxia in different biogeochemical provinces, including estuaries, coastal waters, upwelling areas, fjords and semi-enclosed basins, with various external forcings, ecosystem responses, feedbacks and potential impact on the sustainability of the fishery and economics. The obvious external forcings include freshwater runoff and other factors contributing to stratification, organic matter and nutrient loadings, as well as exchange between coastal and open ocean water masses. Their different interactions set up mechanisms that drive the system towards hypoxia. Coastal systems also vary in their relative susceptibility to hypoxia depending on their physical and geographic settings. It is understood that coastal hypoxia has a profound impact on the sustainability of ecosystems, which can be seen, for example, by the change in the food-web structure and system function; other influences include compression and loss of habitat, as well as changes in organism life cycles and reproduction. In most cases, the ecosystem responds to the low dissolved oxygen in non-linear ways with pronounced feedbacks to other compartments of the Earth System, including those that affect human society. Our knowledge and previous experiences illustrate that there is a need to develop new observational tools and models to support integrated research of biogeochemical dynamics and ecosystem behavior that will improve confidence in remediation management strategies for coastal hypoxia.
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